为探明隧道内自然风对火灾烟气扩散特性的影响，为隧道火灾的通风与排烟系统优化提供科学依据，对云山特长公路隧道洞内自然风进行现场监测，得到洞内自然风分布规律。采用数值模拟方法，建立竖井排烟作用下三维火灾动力学模型，对同向及反向自然风影响下隧道温度场及烟气场进行分析，结果表明： 1）该隧道所处环境的温度能够维持隧道内外相对较大且稳定的热位差，有利于形成自然风，最大自然风速可达5.0 m/s以上。2）在纵向风速3.0
m/s时，同向自然风会扩大隧道温升范围，火源与排烟口之间隧道下部区域温度较低。3）反向自然风会抑制高温场的扩散，且火源与排烟口之间温度随自然风速的增大而升高。4）当隧道内同向自然风速不超过2.5 m/s时火源与排烟口之间烟气质量分数最大，隧道上部空间烟气质量分数大于下部空间。5）当同向自然风速大于3.5 m/s时，下游烟气层结构被破坏，烟气在纵断面内均匀分布。6）反向自然风有利于限制烟气向排烟口下游蔓延，随着自然风的增大，排烟口下游烟气蔓延长度逐渐减小且趋于恒定。7）隧道内同向及反向自然风均会使排烟效率降低，相比无自然风条件，4.0 m/s的同向及反向自然风使竖井排烟效率分别降低22.43%、21.55%，同向自然风对竖井排烟效率的影响程度大于反向自然风。
The authors examine the
effects of natural wind in tunnels on fire smoke diffusion characteristics,
with the aim of providing a scientific basis for optimizing tunnel fire
ventilation and smoke exhaust systems. The natural wind conditions in the
Yunshan extra-long highway tunnel are
monitored on site to determine its distribution pattern. In addition, a three-dimensional fire dynamics model is developed through a numerical
simulation to evaluate the temperature and smoke fields under the influence of
smoke exhaust through a shaft, where the effects of natural wind blowing from
both the same and opposite directions are analyzed. Key findings include: (1)
The ambient temperature in the tunnel maintains a substantial and stable
thermal potential difference between the inside and outside, promoting the
formation of natural wind, with a maximum speed exceeding 5.0 m/s. (2) At a
longitudinal wind speed of 3.0 m/s, natural wind from the same direction increases the range of
temperature rise within the tunnel while lowering the temperature in the lower
section between the fire source and exhaust outlet. (3) The natural wind from
opposite directions inhibits the diffusion of the high-temperature
field, with temperatures between the fire source and smoke outlet rising as
natural wind speed increases. (4) When the natural wind speed from the same
direction does not exceed 2.5 m/s, smoke concentration peaks between the fire source and the smoke
outlet, with higher concentrations in the upper part of the tunnel as compared
to the lower part. (5) At wind speeds exceeding 3.5 m/s from the same
direction, the stratification of downstream flue gas is disrupted, leading to a
more uniform distribution of flue gas. (6) Natural wind from opposite
directions helps to limit the downstream spread of smoke from the exhaust port:
as wind speed increases, the distance that smoke spreads downstream decreases
and approaches a constant value. (7) Both natural wind from the same and
opposite directions reduce smoke exhaust efficiency. Specifically, at a wind
speed of 4.0 m/s, the smoke exhaust efficiency of the shaft decreases by 22.43%
and 21.55%, respectively, compared to conditions without natural wind. The
effects of natural wind from the same direction on the smoke exhaust efficiency
are greater than those of wind from opposite directions.
